Apparatus for contacting solids and gaseous fluids



V April 4, 1950 F H. BLANDING w 2,502,954

APPARATU FOR CONTACTING SOLIDS AND GASEOUS FLUIDS Filed March 9, 1946 2Sheets-Sheet 1 FIG. 2.

. mvsmon FORREST H. BLANDING,

BY y ATTZRNEY- Patented Apr. 4, 1950 APPARATUS FOR CONTACTI NG SOLIDSAND GASEOUS FLUIDS Forrest n. Blanding, Elizabeth. N. 3., assignmtoStandard Oil Develo ration of Delaware pment Company, adorne-Application March 9, 1946, Serial No. sssees 2 Claims. 1

This invention relates to contacting solid par ticles and gaseousfluids, and more particularly,

relates to stripping or purging catalyst or contact particles to removevolatile material therefrom.

In the catalytic conversion of hydrocarbons,-

the catalyst or contact particles become con-' taminated or inactivatedby the deposition of.

coke or hydrogen-containing carbonaceous material on the particles andthe particles must be regenerated, usually by burning with air or otheroxygen-containing gas to remove the coke before returning the catalystparticles to a catalytic conversion zone. Before regeneration it isnecessary to strip or remove volatile hydrocarbons from the particles inorder to reduce the load on the regeneration zone.

In catalytic conversion operations, using finely divided or powderedcatalyst or contact material, the stripping of the spent or contaminatedparticles has recently been an extremely important problem. There aredistinct advantages in such operations in operating at high catalyst tohydrocarbon reed ratios by weight but incomplete stripping of the spentcatalyst or contact particles at these high ratios in present crackingplants causes excessive carbon or coke deposits which usually limits thethroughput of these plants.

Furthermore, extremely high amounts of stripping steam are normally usedas the stripping gas, and it is known that steam has a deactivatingeflect on the catalyst particles. Hence, it is de-" sirable to keep theamount of stripping steam to aminimum.

Also, if incomplete stripping is obtained in a stripping zone or vessel,excess carbon or carboncontaining material is burned in the regenerationJone due to oil vapors entrained with the spent catalyst andcarbonaceous material or coke formed on the catalyst particles due toextensive cracking in the stripping zone of the oil vapors which areentrained into the stripping zone.

According to my invention, the catalyst or contact particles to bestripped are passed from the lower part of a reaction zone or vessel ina relatively dense fluidized liquid-simulating condi; tion into thefirst section of my improved stripping design. This first section is ahigh density settling section having a large cross-sect'onal area inwhich the velocity of the stripping gas is low and wherein the catalystor contact particles during stripping are settled to a high density toexpel a considerable amount oi entrained vapors. Preferably this firstsection contains baflies to in- 2 crease the eiliclency of the strippingzone or vessel.

The catalyst or contact particles being stripped are then passed to anintermediate or high velocity section to strip the particles while theyare maintained in a less dense suspension than ex-= ists in the firststripping section.

The catalyst or contact particles are then passed to a third sectionwhich comprises another high density settling section.

In another form of my invention an auto matically controlled slide valveis provided between the first high density settling section and the highvelocity section to maintain a dilute or disperse phase suspension inthe high velocity section which is less dense than the suspension in theintermediate stripping zone above mentioned in the first form.

In the preferred form of apparatus, the high density stripping sectionforms part of the lower portion of thereaction zone or vessel andcommunicates directly with the high velocity or less dense section whichis arranged directly beneath the first high density settling section;Arranged below the high velocity section is the second high densitysettling section.

The stripped particles are removed from the bottom of the second highdensity stripping section and passed into a standpipe for developingsumcient hydrostatic pressure for passing the stripped spent'particlesto a regeneration zone for regenerating the particles. 2

In the drawings;

Fig. 1 represents one form of apparatus which may be used for carryingout my invention;

Fig. 2 represents a partial horizontal cross-sec tion takensubstantially on line 2-2 of Fig. 1 to show the annular strippingconstruction;

Fig. 3 represents another form of apparatus which may be used forcarrying out my invention in which a slide valve is provided between theupper high density settling section and the lower high velocity section;

Fig. 4 represents a partial horizontal cross-sectional view takensubstantially on line 4 t of Fig. 3 to show another form of annularconstruction for the high density settling section.

Referring now to the drawings, and, more particularly, to Figs. 1 and 2,the reference characterl0 designates a line for introducing hydrocarborfeed or other reactants. Catalyst or contact particles are introducedinto line Ill from standpipe'iZ provided with a control valve 14 forcontrolling the. rate of introduction of catalyst particles into the.line it. The catalyst to oil ratio in fluid catalytic cracking may varybetween about one part of catalyst to one of oil to 40 parts of catalystto one of oil by weight. The standpipe l2 contains hot regeneratedcatalyst particles fed into the standpipe from a regeneration zone (notshown). However, catalyst particles and feed material may be separatelyintroduced into vessel 24. v

The mixture of material to be reacted and the catalyst or contactparticles is passed through line i6 into an inverted cone feed member I8provided in its upper portion with a perforated distribution member orgrid member 22 arranged in thebottom of a reaction vessel 24. The vessel24 is preferably cylindrical and the grid member 22 is circular andarranged concentrically with the vessel 24 in the bottom thereof.

In the catalytic conversion of hydrocarbons, the feed material maycomprise gas oil, heavy naphtha, reduced crude, hydrocarbon oil, etc.The feed may be introduced in the form of vapors or as a partlypreheated liquid containing some vapors. If the feed is only partlypreheated, a suilicient amount of hot regenerated catalyst particles isintroduced into line ID for vaporizing the feed and raising it tocracking or conversion temperature.

The temperature during conversion of hydrocarbons may range from 750 F.to 1050 F. and.

preferably about 925 F. in the catalytic cracking of hydrocarbons toform high anti-knock gasoline. The catalyst in the catalytic cracking ofhydrocarbons may comprise acid-treated bentonites, synthetic silicaalumina gels, synthetic silica magnesia gels, etc. For other hydrocarbonconversion operations, such as catalytic reforming and the like,suitable reforming or other catalysts are used.

The catalyst is preferably in finely divided form having a particle sizebetween about 200 and 400 standard mesh and containing about 0% to 30%by weight of 0 to 20 micron material. The temperature of the hotregenerated catalyst or contact particles in line I2 is about 900 F. to1100 F.

Returnin now to the reaction vessel 24, the hydrotarbon feed andcatalyst particles are introduced into the vessel 24 and the superficialvelocity of the upilowing vapors is selected to maintain the solidparticles in a dense dry fluidized liquid-simulating turbulent conditionshown at 26 and having a level at 28. The superficial velocity is thatvelocity measured with the vessel empty and may be between about 0.5ft./second to 2.0 ft./second. Under these conditions and using the 200to 400 mesh silica-alumina catalyst material above described. thedensity of the fluidized mixture in reactor 24 may vary between about 15lbs/cu. ft. and 35 lbs/cu. ft.

Above the dense mixture 26 is a dilute phase or dilute suspension 32comprising vaporous reaction products containing some entrained catalystparticles. The upper portion of the reaction vessel 24 designated by thereference character 32 comprises a settling section in which thecatalyst particles fall back into the dense mixture 26 so that only adilute suspension or disperse phase 32 is superimposed above the densemixture 26. The density of the dilute suspension in space 32 may varybetween about .005 lb./cu. it. to 1 lb./cu. it. when using the silicaalumina catalyst.

-The vaporous reaction products containing some entrained catalystparticles leave the dilute phase section 32 and are passed intoseparation means 34 through inlet line 38 for removing or separatingmost of the solid particles from the vaporous reaction products. Theseparation means is shown as a cyclone separator arranged in the upperportion of the reaction vessel 24 but other forms of separation devicesmay be used as, for example, Multiclones. If desired, more than oneseparatin stage may be used in series. The separated solid particlescollect in the sep aration means 34 and are returned to the dense bed ormixture 26 through dip pipe 38. The vaporous reaction productssubstantially free of catalyst particles pass overhead through line 42for recovery of desired products. In the catalytic cracking ofhydrocarbons, the vaporous reaction products are passed to afractionation system for recovery of gasoline from other fractions.

During the reaction in the reaction vessel 24, the catalyst or contactparticles become contaminated or partially deactivated by the depositionof coke or hydrogen-containing carbonaceous material thereon. Theparticles are removed irom the reaction vessel 24, stripped and passedto a regeneration zone (not shown) for regenerating the catalystparticles. The partially spent catalyst or contact particles at atemperature of about 750 F. to 1050 F. are preferably withdrawn from thebottom portion oi. the reaction zone as a dense fluidized mixture 24 andpassed into an annular strippin section 44 arranged below thedistribution grid 22 and between a vertical sleeve 48 which depends fromthe distribution plate 22 and the inner wall of the reaction vessel 24.This first stripping section has a relatively large horizontalcross-sectional area and forms a high density low velocity strippingsection. The density 01' the fluidized mixture in stripping section 44is higher than the density 01' the mixture in reactor 24 and there isless turbulence in section 44 than in reactor 24.

With a large cross-sectional area in the stripping zone, the strippingis not as efficient as with a smaller diameter stripping section. Toimprove the stripping of the large cross-sectional area stripping zone,I provide bailles to produce a large number of small diameter cells. Anysuitable form of bafiies may be used, such as a disc and doughnut typeconstruction or an egg crate construction, such as shown in Fig. 2, orother forms 01' baffling to produce a large number of small diametervertical passages.

In Fig. 2 I have shown an egg crate construction in which parallelvertical plates 48 extend from the sleeve 46 to the inner wall of thereaction ve sel 24. Extending at ri ht angles to the parallel plates 48are other plates 52 which form cells 54 in the strip ing zone 44. Theplates extend from the top of the stripping zone 44 as shown in 56 toabout the bottom 58 of the stripping zone. If desired, the plates mayextend further down than shown in the drawing in order to extend thecellular section of the stripping zone.

As above pointed out, the strippin zone 44 has a large cross-sectionalarea and a low velocity oi stripping gas is used in order to maintainthe will make it easier to remove the rest of the volatile material fromthe catalyst particles as they pass downwardly to the next stripping section.

When oil vapors admixed with the spent catalyst enter the stripping zone44, they encounter an extremely severe cracking condition which may beequivalent to a catalyst to oil ratio of 500 and higher because of thehigher density of the mixture in the stripping zone and because 01' lessturbulence. This results in extensive cracking of the entrained oilvapors and considerable amounts of coke or carbonaceous material aredeposited on the catalyst in the stripper. In order to eliminate thiscracking, it is necessary to entrain the least quantity of oil possiblewith the catalyst going into the stripper and to strip these oil vaporsas rapidly as possible so that they will not be cracked extensively.These results are obtained with my high density low velocity settlingstripping section 44. The stripping gas and stripped out material passesupwardly into the dense bed or mixture 26 in the reaction vessel 24.

The sleeve 46 has its bottom portion closed by inverted conical member84 which is concentric with and spaced from the conical bottom 66 of thereaction vessel 24 to form a confined passageway 68 below the strippingsection 44. Small portions of fluidizing gas may be introduced into theconical bottom 66 of the vessel 24 through One or more lines 12 tomaintain the particles in a fluidized condition so'that they flowreadily through the passageway 68 if this is necessary, although usuallythe gas introduced through pipe 13 will accomplish this purpose. Thedense mixture is introduced into the upper portion of a small diameterhigh velocity stripping section 14 provided with a plurality of baflles16. These baflies should preferably be arranged so that there is nodirect vertical passageway through which the catalyst or gas can pass.Stripping gas is introduced through line I3 provided at its inner endwith a plurality of nozzles or outlets for introducing the stripping gasat the base of the high velocity stripping section I4. In the highvelocity section 14, the residual oil vapors not removed in the highdensity section 44 will be removed.

The catalyst or contact material introduced into the upper part of thehigh velocity section 14 is dispersed in the stripping gas and forms aless dense suspension having a density of about 10 lbs/cu. ft. to 25lbs/cu. ft. The superficial velocity of the stripping gas in section 14is about 1 ft./sec. to ft./sec. The less dense phase stripping occurringin the baffled narrow section 14 is very effective in removing entrainedvolatile material from the particles, and in breaking up denseagglomerates of fine particles which entrain hydrocarbon vapors. Thestripping gas and the stripped out material passes upwardly through thefirst stripping section 44 and into the dense bed or mixture 26 in thereaction vessel 24. The stripping gas introduced through line 13 passesup through section l4 and forms the stripping gas introduced into thebottom portion of high density stripping section 44.

From the bottom portion of the narrow high velocity stripping section 14the catalyst or contact particles pass into a third stripping section 88which is another high density low velocity stripping or settlingsection. This third section is shown at 86 in Fig. 1 and while it isshown of an enlarged diameter, may have the same diameter as thestripping section 14. The solid particles are collected in the thirdstripping section 86 as a high density liquid-simulating mixture 88having a level at about the top of pipe 13. However, this level may bevaried. Small quantities of fluidizing and stripping gas are introducedinto the bottom portion of the third stripping section 86 through lines94 and 96 to maintain the particles in a dense fluidized condition whilestripping any residual volatile material therefrom. However, in order toobtain the highest possible density in this section, only the minimumquantity of gas required to keep the catalyst in a fluid suspension isused.

The dense fluidized mixture in the third stripping section 84 has adensity of about 30 lbs/cu. it. to 45 lbs/cu. ft. and the density ishigher than that of the mixture in reactor 24. Also there is lessturbulence in the dense mixture 88 in section 86 than there is in themixture 26 in reactor 24. The superficial velocity of the stripping gaspassing upwardly through the third stripping section 86 is about 0.05ft./second to 0.2 ft./second. The stripping gas and the stripped outmaterial from the top of the third stripping section 86 pass through thenarrow high velocity stripping section 14 and the top high densitystripping section 44 into the dense bed or mixture 26 in the reactionvessel 24. If desired, the stripping gas and stripped out material maybe withdrawn from the upper portion of the intermediate strippingsection, introduced into dust separating means, such as a cycloneseparator, to remove solids and then introduced into the dilutesuspension 32 above the dense mixture 26 in the reaction vessel 24 so asto avoid passage of the hydrocarbon vapors through the dense bed ormixture 26. The separated solids from the separating means (not shown)are preferably returned to the upper end of section 14.

From the high density settling section 86 the stripped spent catalyst orcontact particles are passed into the upper portion of a standpipe 98provided with lines I02 for introducing small amounts of fluidizing gasto maintain the parti cles in a dense dry liquid-like condition in thestandpipe. A suilicient height of standpipe is provided to produce ahydrostatic pressure at the base thereof sufficient to pass theparticles to the regeneration zone (not shown). The standpipe 98 isprovided with a control valve 14 for controlling the rate of withdrawalof spent catalyst particles from the standpipe. The stripped spentparticles are introduced from the standpipe 58 to line- I06 wherein theyare mixed with a regenerating gas, such as air, introduced through lineI08 to form a less dense suspension which is then passed through line H2to the regeneration zone (not shown).

The regeneration zone may be of a structure similar to the reactor 24 orit may take other forms. The regeneration is preferably carried out in adense fluidized condition similar to that above described in connectionwith the reaction vessel 24. The dense fluidized regenerated catalystparticles are preferably withdrawn from the lower portion of aregeneration zone and introacoa'ok's" duce'd' into standpipe l2 forreturn to the reaction vessel 24.

Referring now to Figs. 3 and 4 of the drawing. it will be noted that thegeneral assembly of the apparatus is the same as that described inconnection with Figs. 1 and 2 and the apparatus shown in Figs. 3 and 4will be briefly described except as to those parts which diflfer fromthe showing in Figs. 1 and 2-. In Fig. 3 I have added a slide valvebetween the flrst high density strippingsection and the high velocitystripping section. The valve is preferably automatically con-.

trolled by the level of the dense fluidized mixture contained in thebottom high density stripping section.

The reference character I designates a feed inlet line into whichcatalyst or contact particles are introduced from regenerated catalyststandpipe I22 having a valve I24. The mixture of particles and reactantsis passed through line I28 to inverted cone number I28 having aperforated distribution plate or grid member I32 in its upper portion.The grid I32 is arranged in the bottom portion of the cylindricalreaction vessel I 84.

The particles in the reaction vessel I34 are maintained in a densefluidized turbulent dry liquid-simulating condition shown at I36 havinga level I38 with a dilute or disperse phase I42 superimposed thereabove.A separating means I44 is arranged in the upper portion of the reactionvessel I34 for separating entrained solid particles from vaporousreaction products. The separating means I 44 has an inlet I48. Theseparated solid particles are returned to the dense bed or mixture I38through line I48. Vaporous reaction products pass overhead from theseparating means I 44 through line I 52 and are passed to suitableseparation and recovery equipment.

A high density stripping section I54 is arranged in the lower part ofthe reaction vessel I34. This stripping section is an annular onearranged between sleeve I56 and the inner wall of the reaction vesselI34. The sleeve I56 depends from the distribution plate I32. As pointedout above in the description of Figs. 1 and 2, the initial high densitystripping section has a large cross-sectional area and the velocity ofthe stripping gas passng upwardly therethrough is maintained low tostrip the particles while they are in a dense fluidized condition. Thestripping of such a large cross-sectional area stripping zone isimproved by introducing baflles into the stripping section. Any suitableform of baflling may be used, such as a disc and doughnut typeconstruction, the egg crate construction shown in Figs. 1 and 2, andother baflling may be used.

The battling shown in Fig. 4 differs from that shown in Fig. 3 and willnow be more specifically described.

The baiiled high density stripping section I54 comprises concentricannular members I58 and intersecting radial members I62 to form cellsI64. The members I58 and I62 forming the cells extend from the top I66of the stripping section I54 to the bottom I68 thereof. If desired, themembers may extend further down below the high density stripping sectionI54.

Stripping gas is introduced through one or more lines I10 below thebottom of the stripping section I54. The superficial velocity of thestripping gas is about 0.2 ft./second to 1 ft./second to give a densityin the stripping section I54 of about lbs/cu. ft. to 37 lbs/cu. it.

The dense fluidized stripped material flows down through passageway I'IIbetween the con- 8 4 ical bottom I 12 of vessel I34 and inverted conicalmember I74 which is secured to the bottom pcrlever controller I83 andcontrol means I84. The

control device I83 is responsive to changes in level of the catalyst orcontact particles shown at I88 in the next stripping stage to bepresently 4 described. The catalyst passing from the high densitystripping section is passed through the opening in valve seat I82 to thetop of a narrow high velocity stripping section I88 provided withbaflles, I92. In the high velocity stripping section I88 the catalyst isin a dilute phase or a dilute suspension and very good stripping isobtained under these conditions. The catalyst suspension in theintermediate section I88 is much less dense than the catalyst suspensionin intermediate section 14 in Fig. 1.

The slide valve in its operation permits continuous or intermittentadditions of dense fluidized mixtures of catalyst or contact particlainto the upper part of the high velocity stripping section I88. Theslide valve minimizes circulation of catalyst between the top strippingsection vessel I84 and the dilute phase stripping section. It permitsthe catalyst to be dropped in a dilute phase onto the baflles, where thegas-particle agglomerates are broken up.

A pipe I90 connects the upper portion of stripping section I88 with thetop of the reactor I34 and communicates with the dilute phase sectionI42 in the' reactor. The pipe I90 allows vapors and gases introducedinto the lower portion of stripping section I 88 to escape from the topof the section I88. The pipe is necessary because a pressure drop isobtained across valve I18, the pressure below the valve being less thanthe pressure above the valve. Solids entrained in the gaseous fluidpassing through line I are separated to some extent in settling spaceI42 where the velocity of the gas is decreased and further separated inseparating means I44 in the top of reaction vessel I34.

The stripped particles are collected in a third high density strippingsection I93 as a dense fluidized mass I94 having a level as abovedescribed at I86. Stripping gas for section I88 is passed through line I06 provided with outlets or nozzles I91 below the level I86 of the densefluidized mixture. In this way, the stripping gas will be more evenlydistributed across the area of the high velocity stripping section I88.

The superficial velocity of the stripping gas in intermediate strippingsection I88 is between about 1.5 and 5 it./second. The level I86 isselected as desired and is maintained by level control means I83 and I84 associated with slide valve I18 for regulating passage of catalystfrom stripping zone I54 to stripping zone I88.

Small amounts of additional stripping gas are introduced through lineI98 having outlets or nozzle members 202 arranged in the bottom portionof the dense mixture I84. The superficial velocity of the upflowingstripping gas in the high density stripping section I93 is about 0.05it./second to 0.2 ft./sec0nd. The density of the Any form of battles maybe uscdf 9 fluidized mixture IS! in section I is about 30 lbs/cu. it. to45 lbs/cu. it.

The bottom portion of the last-mentioned high density stripping sectionI93 has a converging bottom or conical bottom 204. The dense fluidizedstripped material is introduced into the upper part of a standpipe 206provided with fluidizing lines 208 for maintaining the particles in afluidized liquid-simulating condition in the standpipe. The standpipe206 is provided with a control valve 2!? at its bottom portion forfeeding spent stripped particles into line 2 where they are mixed with aregenerating gas introduced through line 266 and the resulting mixtureis passed through line 2l8 to a regeneration zone (not shown) In bothforms of my invention shown in Figs. 1 and 3, the downward flow ofcatalyst through the first high density stripping section as, forexample, section 44, is about 100-300 lbs/sq. fir/minute. The downwardflow oi the particles in the high velocity stripping section as, forexample, section it, is about 200-1000 lbs. of particles per square footper minute. The downward flow of particles in the second high densitystripping section 86 is about 100-1000 lbs. of particles per square footper minute.

A theoretical minimum of one volume of stripping gas per volume of gasassociated with the catalyst or contact particles is required toaccomplish good stripping. In usual operations, the stripping gas isused between about one and two volumes of stripping gas per volume ofvolatile material associated with the particles. In my invention, byusing the settling sections, smaller amounts oi stripping gas, such assteam, will be used because of the smaller volume of volatile materialassociated with the catalyst or contact particles.

If desired, more baiiies may be placed in the upper part of section E08nearest the slide valve lid to prevent any excessive flow of catalystdown through the high density settling section I54 at this point.

In a commercial design where the reaction vessel Z8 is about 23 it. indiameter, the annular stripping section til has an inner diameter ofabout 15 ft. The initial high density stripping section 44 may be from 2to 15 ft. in height, preferably about 8 it. The bathing in the highdensity stripping section it may be such as to provide cells 12" indiameter and smaller, and preferably as small as 3" in diameter. Thehigh velocity narrow stripping section l6 may be about to 20 it. inheight, preferably about 15 ft.

The level I86 of the dense phase catalyst l94 is about 10 to feet belowslide valve H8.

While I have shown a certain type of baiiling in Fig. 1, it is to beunderstood that disc and doughnut baflles may be used or a Venetianblind type of battle may be used in this high velocity stripping sectionand also in the same section shown in Fig. 3.

The dense mixture in the bottom of the second high density strippingsection i88 should be about 3 it. to 10 ft. in height.

While I have described my invention more specifically in connection withthe catalytic conversion of hydrocarbons, it is to be understood that myinvention may be used in other processes, such as distillation of oilfrom shale, hydroforming by the fluid technique, Fischer synthesis,carbonization of coal, etc., in which it is desired to remove as much ofthe entrained volatile material as possible from finely divided contactmaterial.

While I have shown the grid (22 in Fig. 1 and I32 in Fig. 3) as beingcircular and centrally located in the bottom of the reactor with thedense stripping zone (44 in Fig. 1 and I5 1 in Fig. 3) in the annularspace around the grid, it is within the contemplation of my invention tohave the grid in the annular space for introducing the catalystparticles and gaseous fluid and have the dense phase stripping andsettling section in the center and lower part of the reactor as acircular central well or draw-off line. In this modification the centralcircular dense phase stripping and settling section has a relativelylarge horizontal cross sectional area to form a high density lowvelocity stripping section as above described in connection with Figs. 1and 3.

While I have disclosed several forms of apparatus and have set forthconditions for converting hydrocarbons, it is to be understood that myinvention is not to berestricted thereto as modifications and changesmay be made without departing from the spirit of my invention.

I claim:

1. An apparatus of the character described including a cylindricalvessel having a top outlet for gaseous fluid, means for introducingsolids and gaseous fluid into the lower central part of said'vessel, anannular strippin section arranged in the lower portion of the saidvessel and surrounding said first-mentioned means for stripping solidswithdrawn from the lower portion of said vessel, means for conductingsolids from said first stripping section to the upper portion of asecond vertically arranged stripping section, a valve between said firstand second stripping sections, said second stripping section beingarranged below said first, stripping section, said second strippingsection being provided with spaced baffles, means for introducingstripping gas into the bottom portion of said first-mentioned andsecond-mentioned stripping sections, means for withdrawing gas from topof secondmentioned stripping section, a third stripping sectioncommunicating at its upper portion with the bottom of said secondstripping section for receiving stripped solids'from said secondsection, means for introducing a stripping gas at a reduced velocityinto said third stripping section to maintain the solid particles in adense fluidized condition therein, means for Withdrawing strippedsolidsfrom the bottom portion of said third stripping section and controlmeans associated with said valve actuated in response to changes in thelevel of the dense bed in said third stripping section to close saidvalve when said level rises and to open said valve when said levelfalls.

2. An apparatus of the character described including a cylindricalvessel having a top outlet for gaseous fluid, means for introducingsolids and gaseous fluid into said vessel arranged centrally of saidvessel, an annular stripping section for stripping solids during passagefrom the bottom portion of said vessel arranged in the low= er portionof the said vessel and surrounding said means for introducing solids andgaseous fluid into the cylindrical vessel, bafile members arranged insaid annular stripping section, means for conducting solids from saidfirst stripping section to the upper portion of a second verticallyarranged stripping section, said second stripping section having asmaller diameter than said first stripping section and being arrangedbelow said first stripping section, said second stripping section beingprovided with spaced baf- 11 fies. means for introducing stripping gasinto the bottom portion oi. said first-mentioned and said thirdstripping section and means for withdrawing stripped solids from thebottom portion of said third stripping section and for passing thewithdrawn solids to said standpipe.

FORREST H. BLANDING. ll

REFERENCES crrsn The following references are of record in the tile ofthis patent:

UNITED STATES PATENTS Number Name Date 2,326,705 Thiele et a1 Aug. 10,1943 2,367,694 Bnuggs Jan. 23, 1945 2,391,836 Ogorzaly Dec. 18, 19452,391,944 Carlsmith Jan. 1, 1946 I 2,394,814 Bnuggs Feb. 12, 19462,440,620 Tail Apr. 27, 1948

1. AN APPARATUS OF THE CHARACTER DESCRIBED INCLUDING A CYLINDRICALVESSEL A TOP OUTLET FOR GASEOUS FLUID, MEANS FOR INTRODUCING SOLIDS ANDGASEOUS FLUID INTO THE LOWER CENTRAL PART OF SAID VESSEL, AN ANNULARSTRIPPING SECTION ARRANGED IN THE LOWER PORTION OF THE SAID VESSEL ANDSURROUNDING SAID FIRST-MENTIONED MEANS FOR STRIPPING SOLIDS WITHDRAWNFROM THE LOWER PORTION OF SAID VESSEL, MEANS FOR CONDUCTING SOLIDS FROMSAID FIRST STRIPPING SECTION TO THE UPPER PORTION OF A SECOND VERTICALLYARRANGED STRIPPING SECTION, A VALVE BETWEEN SAID FIRST AND SECONDSTRIPPING SECTIONS, SAID SECOND STRIPPING SECTION BEING ARRANGED BELOWSAID FIRST STRIPPING SECTION, SAID SECOND STRIPPING SECTION BEINGPROVIDED WITH SPACED BAFFLES, MEANS FOR INTRODUCING STRIPPING GAS INTOTHE BOTTOM PORTION OF SAID FIRST-MENTIONED AND SECOND-MENTIONEDSTRIPPING SECTIONS, MEANS FOR WITHDRAWING GAS FROM TOP OFSECONDMENTIONED STRIPPING SECTION, A THIRD STRIPPING SECTIONCOMMUNICATING AT ITS UPPER PORTION WITH THE BOTTOM OF SAID SECONDSTRIPPING SECTION FOR RECEIVING STRIPPED SOLIDS FROM SAID SECONDSECTION, MEANS FOR INTRODUCING A STRIPPING GAS AT A REDUCED VELOCITYINTO SAID THIRD STRIPPING SECTION TO MAINTAIN THE SOLID PARTICLES IN ADENSE FLUIDIZED CONDITION THEREIN, MEANS FOR WITHDRAWING STRIPPED SOLIDSFROM THE BOTTOM PORTION OF SAID THIRD STRIPPING SECTION AND CONTROLMEANS ASSOCIATED WITH SAID VALVE ACTUATED IN RESPONSE TO CHANGES IN THELEVEL OF THE DENSE BED IN SAID THIRD STRIPPING SECTION TO CLOSE SAIDVALVE WHEN SAID LEVEL RISES AND TO OPEN SAID VALVE WHEN SAID LEVELFALLS.